qeth: avoid crash in case of layer mismatch for VSWITCH

For z/VM GuestLAN or VSWITCH devices the transport layer is
configured in z/VM. The layer2 attribute of a participating Linux
device has to match the z/VM definition. In case of a mismatch
Linux currently crashes in qeth recovery due to a reference to the
not yet existing net_device.
Solution: add a check for existence of net_device and add a message
pointing to the mismatch of layer definitions in Linux and z/VM.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
index 2c48591ced44..21627ba3093b 100644
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -1126,9 +1126,11 @@ static int qeth_l2_recover(void *ptr)
                 dev_info(&card->gdev->dev,
                         "Device successfully recovered!\n");
         else {
-                rtnl_lock();
-                dev_close(card->dev);
-                rtnl_unlock();
+                if (card->dev) {
+                        rtnl_lock();
+                        dev_close(card->dev);
+                        rtnl_unlock();
+                }
                 dev_warn(&card->gdev->dev, "The qeth device driver "
                         "failed to recover an error on the device\n");
         }